From the description:
The writings of our Sages, which reveal various faculties of the soul, help us to take a deeper look into ourselves. We can align our personalities with the will of Hashem through in-depth study and understanding of these faculties, which are common to all people. This sefer has two sections. The first explains the elements of fire, wind, water and earth which correspond to the four fundamental traits in the personality. The second section explains the 13 basic faculties of the soul.
The book is currently available online at Eichler’s. In fact, my wife just bought a copy for me today in Brooklyn. 🙂